Spitzer and colleagues (1) do not show any effect on erection by the addition of testosterone in men treated for ED with the PDE5 inhibitor sildenafil. The study is well-designed, but we believe that it misses some critical points that are milestones in the field.

First, as stated in the Discussion section, an increase in testosterone levels of 3.47 nmol/L (100 ng/dL) occurred during the sildenafil run-in period alone. This is expected when a man with ED resumes sexual activity. Carosa and associates (2) suggested this finding by showing that the increase is not a direct effect of PDE5 inhibitor therapy but instead is mediated by a neuroendocrine response occurring with recovered sexual motivation.